Driftnets are gillnets that are allowed to drift near the surface of the water. Fish are trapped as nets slide behind their gill covers. Driftnets are used to capture many types of fish including tuna, swordfish and salmon. These nets were traditionally small in size, biodegradable and attached to small vessels. Present day driftnets, however, are made of nylon and can measure up to 50km in length. The tops of driftnets are equipped with floats, and weights are attached to the bottoms - creating a vertical wall in the water.
Being non-selective, vast numbers of non-target animals perish in driftnets as bycatch. In some cases, several days pass before the driftnets are retrieved - too late for air breathing mammals caught in the nets to be freed. Unintended victims of driftnets include whales, dolphins, sea turtles, seals, sea lions and seabirds. Some of the victims are endangered species.
Driftnets are particularly dangerous when they become "ghost nets" that have been abandoned or lost by fisherman. Since the nets are made out of highly resistant nylon, they can linger in the environment, entangling marine life for months.
In 2001 the National Oceanographic and Atmospheric Agency (NOAA), created the Pacific Leatherback Conservation Area, prohibiting driftnet fishing for a part of the year in the waters off Monterey, California to the mid-Oregon coast. This decision was a much needed lifeline for leatherback sea turtles, who are still recovering from decades of decline, as well as other marine species. Because of their destructive power, driftnets have also been banned in the European Union since 2002 and in the Baltic Sea. Unfortunately, despite the E.U. ban, French and Italian fisherman continue to illegally use driftnets to catch tuna and swordfish in the Mediterranean Sea, encouraged by the extremely lax enforcement of the ban.
Gillnet fisheries are also responsible for the decline of the most endangered porpoise in the world, the vaquita, a harbor porpoise endemic to the Gulf of California - currently listed as endangered under the U.S. Endangered Species Act (ESA) and Critically Endangered by the World Conservation Union's (IUCN) Red List of Threatened Species.